net: nrf_provisioning: Don't dead-block on send failure

When sending a response, a coap_client might fail.
Don't dead-block, but instead return the error to upper layer.

If sending of response failed while we kept the socket open,
try reconnecting the DTLS session. This allows falling back from
IPv6 to IPv4.

Signed-off-by: Seppo Takalo <[email protected]>

Author: SeppoTakalo

subsys/net/lib/nrf_provisioning/src/nrf_provisioning_coap.c

@@ -309,6 +309,7 @@ static int send_coap_request(struct coap_client *client, uint8_t method, const c
 			     const uint8_t *payload, size_t len,
 			     struct nrf_provisioning_coap_context *const coap_ctx, bool confirmable)
 {
+	int ret;
 	int retries = 0;
 	struct coap_transmission_parameters params = coap_get_transmission_parameters();
 	static struct coap_client_option block2_option;
@@ -336,18 +337,21 @@ static int send_coap_request(struct coap_client *client, uint8_t method, const c
 		client_request.num_options = 1;
 	}
 
-	while (coap_client_req(client, coap_ctx->connect_socket, NULL, &client_request, NULL) ==
-	       -EAGAIN) {
+	while ((ret = coap_client_req(client, coap_ctx->connect_socket, NULL, &client_request,
+				      NULL)) == -EAGAIN) {
 		if (retries > RETRY_AMOUNT) {
 			break;
 		}
 		LOG_DBG("CoAP client busy");
 		k_sleep(K_MSEC(params.ack_timeout));
 		retries++;
 	}
-	k_sem_take(&coap_response, K_FOREVER);
 
-	return 0;
+	if (ret == 0) {
+		return k_sem_take(&coap_response, K_SECONDS(240));
+	}
+
+	return ret;
 }
 
 static int max_token_len(void)
@@ -583,6 +587,7 @@ int nrf_provisioning_coap_req(struct nrf_provisioning_coap_context *const coap_c
 	char *auth_token = NULL;
 	struct cdc_context cdc_ctx;
 	bool finished = false;
+	int retries = 0;
 
 	coap_ctx->rx_buf = rx_buf;
 	coap_ctx->rx_buf_len = sizeof(rx_buf);
@@ -644,7 +649,7 @@ int nrf_provisioning_coap_req(struct nrf_provisioning_coap_context *const coap_c
 				LOG_INF("Finished");
 				finished = true;
 			}
-
+retry_response:
 			if (!socket_keep_open) {
 				ret = socket_connect(&coap_ctx->connect_socket);
 				if (ret < 0) {
@@ -660,6 +665,14 @@ int nrf_provisioning_coap_req(struct nrf_provisioning_coap_context *const coap_c
 			LOG_INF("Sending response to server");
 			ret = send_response(&client, coap_ctx, &cdc_ctx);
 			if (ret < 0) {
+				if (socket_keep_open && retries++ == 0) {
+					/* Try reconnecting */
+					socket_close(&coap_ctx->connect_socket);
+					socket_keep_open = false;
+					goto retry_response;
+				}
+				LOG_ERR("Failed to send response, ret %d", ret);
+
 				break;
 			}
 			/* Provisioning finished */

subsys/net/lib/nrf_provisioning/src/nrf_provisioning_codec.c

@@ -542,6 +542,7 @@ int nrf_provisioning_codec_process_commands(void)
 
 	/* Can't send anything if modem connection is not restored */
 	if (mret < 0) {
+		LOG_ERR("Failed to restore functional mode, error: %d", mret);
 		return mret;
 	}